High-speed digital interfaces have become widespread with modern technology's emphasis on rapid transfer and communication of digital data for an ever-increasing amount of important functions, from video conferencing to data storage. These interfaces include high-speed transmitters for transmitted data at high rates, such as gigabit speeds. A number of types of high-speed transmitters are used in a variety of applications, including current mode logic (CML), voltage mode logic (VML), and others.
The different types of high-speed transmitters have been specified to accommodate practical speed-to-power tradeoffs. One trend is to reduce the performance of a high-speed transmitter in order to keep the power low enough for applications having a high number of input/output (I/O) ports. For the majority of channels the lower performance may be adequate; however, this level of performance may present significant challenges on more difficult channels, such as channels having increased noise and/or having greater physical length. These difficult channels may in some cases require a separate re-driver or repeater component to improve transmitter and receiver performance.
In most communications devices, high speed transmitters can either be efficient with lower performance and lower power consumption, or be powerful with higher performance and higher power consumption. Rarely can transmitters be both efficient and powerful. Therefore, for example, a designer must pick one option early in the design process of a transmitter, to either use an efficient type of transmitter (such as VML) for appropriate conditions such as short transmission distances, or to use a higher-amplitude, powerful transmitter type (such as CML) for conditions such as long transmission distances or otherwise difficult channels. These restrictions allow little flexibility in the eventual use and applications of devices using these transmitters.
These and other limitations of the prior art will become apparent to those of skill in the art upon a reading of the following descriptions and a study of the several figures of the drawing.